In a long-term evolution (LTE) system, in order that a base station indicates an appropriate transmission power control command to user equipment, an appropriate modulation and coding scheme and bandwidth are scheduled for the user equipment, the user equipment needs to measure its power headroom (PH) and report the PH to the base station. Wherein, the PH is a difference between configured maximum output power (PCMAX) of the user equipment and the current transmission power.
In the LTE system, as the range of error between the configured maximum output power actually used in transmitting uplink data by the user equipment and the configured maximum output power used by the user equipment that is estimated by the base station is relatively small, in a power headroom report (PHR), the user equipment needs only report the PH, and the configured maximum output power is estimated by the base station itself.
In an LTE-advanced (LTE-A) system, as a carrier aggregation technology is used, when user equipment transmits uplink data in multiple serving cells simultaneously, if the configured maximum output power used by the user equipment is still estimated by a base station, there would be a relatively large difference between the configured maximum output power obtained by the base station through estimation and the configured maximum output power actually used by the user equipment, which will have effect on the base station in scheduling resources for the user equipment.
Currently, in an LTE-A system, in order to avoid the above effect, when the user equipment reports a PHR, besides the PHR, a configured maximum output power PCMAX needs also to be reported under a certain condition.
Wherein, when the user equipment is configured with multiple serving cells, if the user equipment triggers a PHR and the PHR may be contained by an uplink resource allocated by the base station to the user equipment, the user equipment will simultaneously report all the PHs in serving cells in activated states and configured with uplink carriers; while according to provisions in protocols, the user equipment reports only the configured maximum output power PCMAX to which a serving cell having valid uplink grant corresponds. For a serving cell having no uplink grant, in order to obtain the PH of the serving cell, reference values of parameters needing to be used in calculating the PH are defined in the protocols. According to the reference values defined in the protocols, the base station may accurately calculate the configured maximum output power PCMAX used by the user equipment in each serving cell having no uplink grant.
However, in the implementation of the present invention, the inventors found that following defect exists in the prior art: if the user equipment has no valid uplink grant in at least one serving cell, but there exists actual physical transmission in the serving cell, such as uplink no-adaptive retransmission, or the base station schedules only channel station information, the user equipment cannot report the configured maximum output power PCMAX to which the serving cell corresponds. However, the user equipment will have actual configured maximum output power PCMAX in the serving cell. In such a case, if the base station calculates the configured maximum output power PCMAX in the serving cell according to the reference values defined in the protocols, there will be a relatively large error between the configured maximum output power PCMAX obtained through calculation and the actual configured maximum output power, which will have effect on the subsequent control of the transmission power of the user equipment by the base station in the serving cell, as well as determination of its modulation and coding scheme and bandwidth scheduling. There has no solution for the above defect till now.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.